Date of Submission

5-12-2025

Document Type

Thesis

Degree Name

Master of Science in Forensic Technology

Department

Forensic Science

Advisor

Josep De Alcaraz-Fossoul, Ph.D.

Committee Member

Brooke W. Kammrath, Ph.D.

Committee Member

Kevin Parisi, Ph.D.

Keywords

Latent Fingermark (LF) Age Estimation, Topographical Changes, 2D and 3D Techniques, Sebaceous-Rich LFs, Latent Fingermark Degradation, Aging Parameters

MeSH

Aging

LCSH

Fingerprints

Abstract

Latent fingermark (LF) age estimation remains a challenging and unresolved issue in forensic science. Latent friction skin ridge impressions are dynamic three-dimensional (3D) structures that undergo time-dependent changes in their topography, a process referred to as aging. These changes can be measured using both two-dimensional (2D) and 3D techniques, which are able to capture changes in color contrast between ridges and furrows, as well as an alteration in ridge height and volume over time. Various factors, including physical, biological, and environmental influences, contribute to the rate and extent of LF degradation. Recent research has emphasized non-destructive, fast, and portable optical techniques as approaches to aging studies. To date, there is no standardized optical method to estimate the age of LFs or the changes that occur after deposition. Understanding how temporal and environmental processes influence the topography of ridges is critical, as they could contribute to the overall aging patterns. Establishing these patterns could help determine the time frame in which a crime was committed, potentially linking a suspect to the scene.

This study sought to document and evaluate the topographical changes in LFs over time once placed in depletion series of 15 on a glass surface and aged in complete darkness at four intervals: days 0, 5, 13, and 27 post-deposition. Two imaging techniques were employed: a conventional 2D method using black magnetic powder and photography, and a microscopic 3D technique with an optical profilometer (OP). Sebaceous-rich LFs from four healthy adult males were collected in triplicate from the index finger and thumb of the dominant hand. A total of 1,440 LFs were deposited with medium pressure and images were collected under monitored environmental and lighting conditions. The 2D analysis provided data on color contrast (CC metric) and ridge clarity (BG metric). The 3D analysis measured microscopic data along the x, y, and z axes, specifically ridge height (Sa metric) and volume (Vu metric). The analysis included normalization and regression analysis with Microsoft Excel®. Additional tests included box plots to examine data distribution, identification of outliers, and univariate and multivariate analyses performed with IBM SPSS® Statistics 25. Principal component analysis (PCA) was also performed to reduce the large dataset dimensionality and identify correlations among metrics.

Results revealed distinct patterns of degradation across the aging parameters. Sa and Vu, demonstrated stronger sensitivity to depletion-driven changes in the early stages, with clear differences observed shortly after deposition. By contrast, the BG and CC were more influenced by aging, with BG showing continuous decline and CC becoming more sensitive to degradation after Day 13. Multivariate analyses (MANOVA) indicated that depletion introduced greater variability in LF degradation compared to aging alone, with Sa and Vu exhibiting strong correlations across time points. PCA revealed that Sa and Vu clustered closely, while BG and CC showed moderate and high separation, respectively, confirming the different degradation patterns captured by 2D and 3D metrics. These findings underscore the value of combining 2D and 3D techniques to assess LF age and degradation over time, in which 3D metrics show promise for detecting early degradation, while 2D metrics may be more suited for long-term aging assessments.

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Available for download on Monday, May 10, 2027

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